Physics
Physics
Problem
A block of mass is pulled up a rough inclined plane of angle with the horizontal at constant speed. The pulling force is applied by a light string parallel to the plane. The coefficient of kinetic friction between the block and the plane is . The block is moved a distance along the incline. a. (i) Draw a labelled free-body diagram showing all the forces acting on the block while it is being pulled up the plane. b. (ii) Obtain expressions for the work done, in terms of the given symbols, by (a) the tension , (b) the component of the block’s weight along the plane, (c) the normal reaction, and (d) the force of kinetic friction during the displacement . c. (iii) Hence show that the net work done on the block is zero and explain why this result is consistent with the block moving at constant speed.Intuitive explanation
The key here is recognizing that constant speed means zero acceleration, so all forces must be balanced—this is an equilibrium problem, not a dynamics one. Set up your force balance along and perpendicular to the incline: the tension must overcome both the component of gravity pulling the block down the slope and the friction force opposing motion. Once you find , you can calculate the work done by each force, paying careful attention to which forces actually do work on the block over distance .
Intuitive explanation
The key here is recognizing that constant speed means zero acceleration, so all forces must be balanced—this is an equilibrium problem, not a dynamics one. Set up your force balance along and perpendicular to the incline: the tension must overcome both the component of gravity pulling the block down the slope and the friction force opposing motion. Once you find , you can calculate the work done by each force, paying careful attention to which forces actually do work on the block over distance .